Overlay sheet and process for making the same



United States Patent 3,365,354 OVERLAY SHEET AND PROCESS FOR MAKING THESAME Peter N. Britton, Scotch Plains, N.J., assignor to Johnson &Johnson, a corporation of New Jersey No Drawing. Grigiual appiicatiouAug. 7, 1963, Ser. No. 300,648. Divided and this appiication Jan. 30,1967, Ser. No. 612,346

12 Claims. (Cl. 161-150) ABSTRACT OF THE DISCLOSURE This inventionrelates to the treating of a nonwoven web of substantially 100% acrylicfibers with a solution of dimethyl sulfoxide to facilitate autogenicbonding of such web to provide a nonwoven overlay sheet.

This is a division of application Ser. No. 300,648 filed Aug. 7, 1963.

Decorative laminates generally comprise a base material, Which may besuperimposed layers of synthetic resinimpregnated paper or a sheet ofchipboard, plywood, etc., on top of which is placed a decorative sheet.The decorative sheet may be a synthetic resin-impregnated decorativepaper, i.e., a paper having a wood-like grain, metal flecks or otherdesign, or a wood veneer, or similar materials. On top of the decorativesheet is placed a synthetic resinimpregnated overlay sheet. Heat andpressure are applied to the laminate to compress and fuse the plies(base material, decorative sheet and overlay sheet) into a dense solidsheet which is used for counter tops, wall paneling, etc.

In the final laminate the overlay sheet is transparent to the eye sothat in net effect the appearance of the laminate is similar to theappearance of the decorative sheet. The overlay sheet protects thedecorative sheet during use and for this purpose it must be tough,abrasion-resistant and resistant to solvents, heat, water, etc.

It is important in such overlay sheets that they be extremely uniform inconstruction, contain virtually no impurities, be relatively inert tothe eiiects of heat and humidity, etc.

The overlay sheets of the present invention consist entirely or almostentirely of acrylic fibers united at their points of intersection withadjacent fibers to form a unitary sheet. The sheet has a denseconstruction which is uniform over the entire area of the sheet andthroughout the thickness of the sheet. The unitary acrylic fiber sheethas good strength, is tough, abrasion-resistant and resistant to heat,water, etc. The surface of the acrylic fiber sheet is smooth and hassubstantially no loose ends of fibers sticking out of the plane of thesheet.

In accordance with the present invention the overlay sheet is made byforming a web of 100% acrylic fibers. The fibers in the web are inoverlapping and intersecting relationship. The fibrous web is treatedwith an aqueous solution of dimethyl sulfoxide. The web containing thedimethyl sulfoxide is heated while the web is confined, i.e., underslight pressure on both outer surfaces to activate the dimethylsulfoxide, remove the water and produce a unitary sheet of autogenicallybonded 100% acrylic fibers. Preferably, the autogenically bonded acrylicfiber fabric is treated a second time with a weaker aqueous solution ofdimethyl sulfoxide and again heated, while the treated fabric isconfined, to dry the fabric and produce a 100% acrylic fiber fabrichaving smooth outer surfaces.

The use of the acrylic fibers is important because with such fibers, inaccordance with the method of the invention there is obtained a fabricwhich does not contain neps or clumps of fibers and which issubstantially uniform in thickness and has a uniform distribution offibers over its entire area. The decorative laminate made with theoverlay sheet of the invention has a uniform, smooth, glossy,transparent surface which is resistant to water, solvents and heat, andis tough and resistant to abrasion.

The acrylic fibers used in accordance with the invention have about thesame index. of refraction as the resins. Accordingly, in the finisheddecorative laminates the overlay sheets of the invention are transparentto the eye.

The acrylic fibers which are suitable for use in accordance with theinvention are those fibers which are composed of at least by weight ofacrylonitrile units. Suitable examples are Orlon, Acrilan, Verel, etc.The acrylic fibers are unpigmented and have a denier of from about 1 to10. The length of the acrylic fiber may range from about 1 to 2 inchesor more.

The web of acrylic fibers may be formed by any of the conventionalmethods known in the art. Suitable examples of such methods are carding,air-laying, water-laying, etc. In the web the acrylic fibers are inoverlapping, intersecting relationship and the fibers may be oriented inone or more directions or randomly oriented.

The overlapping, intersecting fibers are held together by beingautogenically bonded to adjacent fibers. By autogenic bonding it ismeant that fibers are adhered to adjacent fibers by softening the areasof contact between fibers and allowing the fibers to adhere without theuse of any outside adhesive agent. In accordance with the presentinvention the use of autogenic bonding eliminates any material otherthan acrylic fibers from being in the final product, hence the finalproduct is completely uniform in both chemical and physicalcharacteristics.

Methods of autogenically bonding synthetic fibers are well-known in theart; for example, if the fibers are thermoplastic in nature they may besoftened and adhered by the application of heat and pressure. Othermethods of autogenic bonding are to apply weak solutions of solvents orswelling agents to the fibrous material to soften the surface of thefibers and adhere them together. However, when autbgenically bondingacrylic fibers the use of heat often melts the fiber and causes it tolose many of its fibrous characteristics. Similar loss of fibrouscharacteristics will occur when many of the known solvents for acrylicfibers are used as autogenic bonding agents. For example, when dimethylformamide is used to autogenically bond a web of acrylic fibers iteither produces a weak bond or if sufficient dimethyl formamide is usedto produce a good bond pinholes are burned in the Web making the finalfabric non-uniform and unsuitable for use as an overlay sheet.

One of the better known solvents and autogenic bonding agents foracrylic fibers are the carbonates such as ethylene carbonate, propylenecarbonate, etc. Though these agents produce a well-bonded acrylic fibersheet they also render the sheet sensitive to water and humidity and ifsuch a sheet is used in a decorative laminate the resultant productreadily water spots when placed in contact with water.

In accordance with the present invention an acrylic fiber sheet may bewell-bonded, maintain uniformity and its water resistance and beespecially suitable for use as an overlay sheet in decorative laminatesif the acrylic fibers are autogenically bonded with aqueous solutions ofdimethyl sulfoxide. The aqueous solutions of dimethyl sulfoxide used inaccordance with the invention contain from about 2% to 20% by weight ofdimethyl sulfoxide and preferably from about 3% to 12% by weight ofdimethyl sulfoxide. If a concentration of less than about 2% dimethylsulfoxide is used the resultant fabric is poorly bonded and does nothave the required strength of an overlay sheet. If more than about 20%dimethyl sulfoxide is used pinholes are burned in the web and theuniformity of the web greatly disrupted.

The aqueous solution of dimethyl sulfoxide may be applied to the web ofacrylic fibers by any of the conventional techniques known in the artsuch as spraying, padding, saturating, etc. It is important that thebinder be uniformly applied to obtain uniform bonding and prevent highconcentrations of dimethyl sulfoxide in some areas and lowconcentrations of dimethyl sulfoxide in other areas.

The web containing the dimethyl sulfoxide is then dried by heating theweb to a temperature of from about 212 F. to 400 F. or higher for aperiod of time of from about 30 seconds to minutes or more.

It is preferred that when the web is being dried it be confined, i.e.,it be under slight pressure on both surfaces of the web. It appears thatthe confinement of the web while being dried is very important in orderto produce a well-bonded fabric of high uniformity. It is believed thatthe confinement uniformly distributes the dimethyl sulfoxide throughoutthe web and maintains it in intimate contact with the acrylic fibersduring the drying to produce a uniformly bonded web.

Acrylic fibers like many synthetic fibers are resilient and whencompressed will flatten out but when the pressure is released willspring back to their original position. The application of the aqueoussolution of binder flattens and compresses the acrylic fibers but as thewater is removed the acrylic fibers tend to spring out of theircompressed state. Placing the web containing the dimethyl sulfoxide in aconfined state and drying the web while so confined produces a smoothwell-bonded fabric. Furthermore, the confinement of the web densifiesthe web to produce a strong fabric with a uniform fiber distribution.

Suitable methods of drying the web containing the dimethyl sulfoxidewhile in the confined state are to place the web between a pair of beltsand pass the belts with the fabric therebetween into an atmosphere at anelevated temperature to drive off the water, bond the fibers, and drythe fabric. Another suitable method is to pass a continuous belt about astack of dry cans, cans heated from the inside by steam or other meansso that their surface is heated. A number of dry cans are placed in arow or a series of rows to form a stack, and a belt of cotton duck orsimilar material passed in serpentine fashion from the surface of onecan to the surface of the adjacent can. The fabric is to be dried isplaced between the belt and can surface and is passed from can to canalong with the belt in such a manner that the fabric is pressed againstthe heated surface of every other can to drive off water, bond thefibers, and dry the fabric.

It is preferred that after the autogenically bonded acrylic fiber fabricis formed it be treated a second time to remove loose ends of fiberswhich stick out from the general plane of the fabric. This may beaccomplished by treating the fabric with a weak aqueous solution ofdimethyl sulfoxide of from about 2% to 5% by weight of dimethylsulfoxide and preferably from about 2% to about 3% by weight dimethylsulfoxide. The dimethyl sulfoxide may be applied to the bonded fabric byany of the techniques previously described for applying autogenicbinders to fibrous webs.

The treated fabric is again dried at temperatures of from about 212 F.to 400 F. for a period of time of from about 30 seconds to 5 minutes. Itis preferred that the fabric be dried the second time also in a confinedstate as previously described.

If desired, the fabric may be given a third .or even more similartreatments.

The invention will be further illustrated in greater detail by thefollowing examples. The percentages indicated are by weight unlessspecifically stated otherwise.

4 EXAMPLE 1 An air-laid web is formed on a conventional air-layingmachine from 3-denier, 1% inch unpigmented acrylic fibers, sold by theE. I. du Pont Corporation under the trade name Orlon. The web, weighingabout 350 grains per square yard, is passed through a saturating bathcontaining an aqueous solution of 12% dimethyl sulfoxide. The wet pickupis about The saturated web is placed on a cotton duck belt While the webis kept under tension and the belt and web passed about a, stack of drycans at a temperature of about 290 F. The web contacts a portion of thesurface of every other can while the belt contacts the surface of theintermediate cans. The drying operation takes approximately 30 seconds.

The web is passed a second time through a saturating path as describedabove. The second saturation bath contains an aqueous solution of 2%dimethyl sulfoxide and the wet pickup is about 100%. The saturated webis dried as described above to produce the fabric of the invention. Thefinal fabric Weighs about 350 grains per square yard.

A piece of the fabric is used as the overlay sheet of a decorativelaminate using diallyl phthalate resin as the overall impregnatingresin. The laminate is formed by the application of heat and pressure inaccordance with conventional procedures, and the overlay sheet alongwith the resin with which it was impregnated becomes the outer surfaceof the laminate. The surface is transparent and the decorative design isreadily seen without, however, seeing any individual fibers. The surfaceresists abrasion and is very tough, and is not affected by water, heator solvents.

EXAMPLE 2 A card web containing 50%, 3-denier, 1% inch unpigmentedacrylic fibers and 50%, Z-denier, %-inch unpigrnented acrylic fibersweighing about 400 grains per square yard is passed through a saturatingbath containing an aqueous solution of 5% dimethyl sulfoxide. The wetpickup is about 120%.

The saturated web is placed between two cotton duck belts and thesandwich placed in an oven at 240 F. for a period of about 2 minutes.

The Web is passed a second time through a saturating bath as describedabove. The second saturation bath contains an aqueous solution of 3%dimethyl sulfoxide and the wet pickup is about 100%. The saturated webis dried as described above to produce the fabric of the invention. Thefinal fabric weighs about 400 grains per square yard.

The fabric used as the overlay sheet of a decorative laminate givesresults similar to those stated in Example 1.

EXAMPLE 3 An air-laid web containing 100%, 3-denier, 1 /4 inchunpigmented acrylic fibers, sold by the Chemstrand Corporation under thetrade name Acrilan and weighing about 350 grains per square yard ispassed through a saturating bath containing an aqueous solution of 16%dimethyl sulfoxide. The wet pickup is about 120%.

The saturated web is placed on a cotton duck belt while the web is keptunder tension and the belt and web passed about a stack of dry cans at atemperature of about 290 F. The Web contacts a portion of the surface ofevery other can while the belt contacts the surface of the intermediatecans. The drying operation takes approximately 30 seconds and produces awell-bonded fab ric consisting entirely of acrylic fibers.

The fabric used a the overlay sheet of a decorative laminate givesresults similar to those stated in Example 1.

EXAMPLE 4 A card web containing 50%, 3-denier, 1% inch unpigmentedacrylic fibers and 50%, 1 /2 denier, l-inch bright viscose rayon fibersweighing about 350 grains per square yard is autogenically bonded withdimethyl sulfoxide as described in Example 1.

The resultant fabric is passed a second time through a weak solution ofdimethyl sulfoxide and dried to remove loase ends of fibers as describedin Example 1.

A piece of the fabric is used as the overlay sheet of a decorativelaminate using a di-allyl phthalate resin as the over-all impregnatingresin. The laminate is formed by the application of heat and pressure inaccordance with conventional procedures, and the overlay sheet alongwith the resin with which it was impregnated becomes the outer surfaceof the laminate. Individual fibers are seen in the laminate which isdull and the laminate readily clouds over when it comes in contact withwater.

EXAMPLE 5 An air-laid web of 100%, 3-denier, 1% inch unpigmented acrylicfibers is passed through a saturating bath containing an aqueoussolution of dimethyl formamide. The wet pickup is 120%. The saturatedweb is dried as described in Example 1. The resultant fabric is veryweak and is not resistant to water.

A second fabric is made as described above with the exception that thedimethyl formamide i replaced with propylene carbonate. The resultantfabric has good strength but poor water-resistance and when used as theoverlay sheet in a decorative laminate readily clouds and becomes dullwhen Water contacts the surface of the decorative laminate.

The invention is not to be construed as limited by the examplespreviously given nor to the specific features mentioned therein exceptas the same may be included in the claims appended hereto. It isunderstood that changes, modifications and variations may be made in thefabric without departing from the spirit and scope of the claimedinvention.

What is claimed is:

1. A method of manufacturing a tough, Water-resist- ,ant, nonwovenfabric of acrylic fibers which comprises:

forming a fibrous web of 100% substantially unpigrnented acrylic fibers,said fibersbeing in overlapping, intersecting relationship, uniformlyapplying to said web an aqueous solution containing from about 2% toabout by Weight of dimethyl sul-foxide to soften the surface of theacrylic fibers, and drying the treated web to remove the water andadhere adjacent fibers together at their points of intersection wherebya unitary structure consisting of acrylic fibers is formed.

2. A method of manufacturing a tough, water-resistant, nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, impregnating said web with anaqueous solution containing from about 2% to about 20% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, heatingthe treated web in a confined state to remove the water and adhereadjacent fibers together at their points of intersection whereby aunitary structure consisting of acrylic fibers is formed.

3. A method of manufacturing a tough, water-resistant, nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, impregnating said web with anaqueous solution containing from about 2% to about 20% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, heatingthe treated web to remove the Water and adhere adjacent fibers togetherat their points of intersection whereby a unitary structure consistingof acrylic fibers is formed, impregnating said unitary structure with anaqueous solution containing from about 2% to about 5% by weight ofdimethyl sulfoxide and heating the treated structure to remove loosefiber ends on the surface of the unitary structure.

4. A method of manufacturing a tough, water-resistant, nonwoven fabricof acrylic fibers which comprises: forming a fibrous web ofsubstantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, impregnating said web with anaqueous solution containing from about 2% to about 20% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, heatingthe treated web in a confined state to remove the water and adhereadjacent fibers together at their points of intersection whereby aunitary structure consisting of acrylic fibers is formed, impregnatingsaid unitary structure with an aqueous solution containing from about 2%to about 5% by Weight of dimethyl sulfoxide and heating the treatedstructure in a confined state to remove loose fiber ends on the surfaceof the unitary structure.

5. A method of manufacturing a tough, water-resistant, nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 2% to about 20% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, anddrying the treated web in a confined state at a temperature of fromabout 212 F. to 400 F. for a period of time of from about 30 seconds to5 minutes to remove the water and adhere adjacent fibers together attheir points of intersection whereby a unitary structure consisting ofacrylic fibers is formed.

6. A method of manufacturing a tough, water-resistant nonwoven fabric ofacrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 3% to about 12% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, dryingthe treated web in a confined state at a temperature of from about 212F. to 400 F. for a period of time of from about 30 seconds to 5 minutesto remove the water and adhere adjacent fibers together at their pointsof intersection whereby a unitary structure consisting of acrylic fibersis formed.

'7. A method of manufacturing a tough, Water-resistant nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 2% to about 20% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, dryingthe treated Web at a temperature of from about 212 F. to 400 F. for aperiod of time of from about 30 seconds to 5 minutes to remove the waterand adhere adjacent fibers together at their points of intersectionwhereby a unitary structure consisting of acrylic fibers is formed,uniformly applying to said unitary structure an aqueous solutioncontaining from about 2% to about 5% by weight of dimethyl sulfoxide anddrying the treated structure at a temperature of from about 212 F. to400 F. for a period of time of from about 30 seconds to 5 minutes toremove loose fiber ends on the surface of the unitary structure.

:8. A method of manufacturing a tough, water-resistant nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unpigmented acrylic fiber-s, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 3% to about 12% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, dryingthe treated web at a temperature of from about 212 F. to 400 F. for aperiod of time of from about 30 seconds to 5 minutes to remove the waterand adhere adjacent fibers together at their points of intersectionwhereby a unitary structure consisting of acrylic fibers is formed,uniformly applying .to said unitary structure an aqueous solutioncontaining from about 2% to about 3% by weight of dimethyl sulfoxide anddrying the treated structure at a temperature of from about 212 F. to400 F. for a period of time of from about 30 seconds to minutes toremove loose fiber ends on the surface of the unitary structure.

9. A method of manufacturing a tough, water-resistant nonwoven fabric ofacrylic fibers which comprises: forming a fibrous Web of 100%substantially unpigmentcd acrylic fibers, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 2% to about by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, dryingthe treated web in a confined state at a temperature of from about 212F. to 400 F. for a period of time of from about 30 seconds to 5 minutesto remove the water and adhere adjacent fibers together at their pointsof intersection whereby a unitary structure consisting of acrylic fibersis formed, uniformly applying to said unitary structure an aqueoussolution containing from about 2% to about 5% by weight of dimethylsulfoxide and drying the treated structure in a confined state at atemperature of from about 212 F. to 400 F. for a period of time of fromabout 30 seconds to 5 minutes to remove loose fiber ends on the surfaceof the unitary structure.

10. A method of manufacturing a tough, water-resistant nonwoven fabricof acrylic fibers which comprises: forming a fibrous web of 100%substantially unp-igmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, uniformly applying to said weban aqueous solution containing from about 3% to about 12% by weight ofdimethyl sulfoxide to soften the surface of the acrylic fibers, dryingthe treated web in a confined state at a temperature of from about 212F. to 400 F. for a period of time of from about 30 seconds to 5 minutesto remove the water and adhere adjacent fibers together at their pointsof intersection whereby a unitary structure consisting of acrylic fibersis formed, uniformly applying to said unitary structure an aqueoussolution containing from about 2% to about 3% by Weight of dimethylsulfoxide and drying the treated structure in a confined state at atemperature of from about 212 F.

to 400 F. for a period of time of from about 30 seconds to 5 minutes toremove loose fiber ends on the surface of the unitary structure.

11. A method of manufacturing a tough, water-resistant, nonwoven fabricof acrylic fibers which comprises: forming a fibrous web ofsubstantially unpigmented acrylic fibers, said fibers being inoverlapping, intersecting relationship, impregnating said web with anaqueous solution containing about 12% by weight of dimethyl sulfoxide tosoften the surface of the acrylic fibers, drying the treated web in aconfined state at a temperature of from about 240 F. to 300 F. for aperiod of time of from about 30 seconds to 2 minutes to remove the Waterand adhere adjacent fibers together at their points of intersectionwhereby a unitary structure consisting of acrylic fibers is formed,impregnating said unitary structure with an aqueous solution containingabout 2% by weight of dimethyl sulfoxide and drying the treatedstructure in a confined state at a temperature of from about 240 F. to300 F. for a period of time of from about 30 seconds to 2 minutes toremove loose fiber ends on the surface of the unitary structure.

12. The nonwoven fabric made by the process of claim 11.

References Cited UNITED STATES PATENTS 2,784,135 3/1957 Wooding et al.161-251 X 2,920,992 1/1960 Hubbard 162-157 2,986,798 6/1961 Koenig eta1. 28-76 3,010,858 11/1961 Sexsmith 161170 X 3,053,609 9/ 1962 Miller8--128 3,126,297 3/1964 Diamantopoulos 117140 3,143,437 8/1964 Rosset117-1383 3,236,586 2/1966 Humphreys 8130.1 3,236,587 2/1966 Genereux8-130.1 3,253,880 5/1966 Lawson 8-115.5 3,291,561 12/1966 Abashian156-308 X EARL M. BERGERT, Primary Examiner.

HAROLD ANSHER, Examiner.

